User Manual

3UG4625 residual current monitoring relay with 3UL23 transformer
9.3 Functions
3UG4 / 3RR2 monitoring relays
Manual, 02/2013, NEB927043002000/RS-AA/002
189
9.3 Functions
General functionality
3UG4625 residual current monitoring relays are supplied with a rated control supply voltage
of 24 to 240 V AC/DC (rms value), 50/60 Hz via terminals A1+ and A2-.
3UG4625 residual current monitoring relays are equipped with a display and are
parameterized with three keys.
You will find the setting ranges and factory settings of the available parameters in Chapter
"Operation (Page 196)".
You will find a description of the individual parameters in Chapter "
Parameters (Page 351)".
The main conductors and, if present, the neutral conductor to which the load is conne
cted,
are routed through the opening of the ring core of a 3UL23 residual current transformer.
There is a secondary winding around this ring core to which the 3UG4625 residual current
monitoring relay is connected.
In fault-free operation of a system, the sum of inflowing and outflowing currents equals zero.
No current is then induced in the secondary winding of the residual current transformer.
When an insulation error occurs, for example, the sum of the inflowing currents is greater
than the sum of the outflowing currents.
The residual current induces a secondary current in the secondary winding of the
transformer. This current is evaluated in the monitoring relay and used to display the current
residual current and to switch the output relays when the set warning threshold or the
tripping threshold is overshot.
To ensure a maximum plant availability 3UG4625 residual current monitoring relays focus on
the following features:
● High degree of measuring accuracy
3UG4625 residual current monitoring relays in combination with 3UL23 residual current
transformers operate with a measuring accuracy of -7.5 %/+7.5 %. This enables set limit
values to be monitored very precisely. False tripping caused by measuring errors is
minimized.
● Adjustable delay times
The ON-delay time of 3UG4625 residual current monitoring relays can be configured
freely, enabling fading out of fault currents due to high input currents that are measured
during motor start-up only. Short-term fault currents or emitted interference can be easily
faded out using the adjustable tripping delay time. For more information please see the
Chapter "Measuring accuracy (Page 189)".